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1
Evans, Philip. "Friction on Frictions". Physiotherapy 78, n. 12 (dicembre 1992): 930. http://dx.doi.org/10.1016/s0031-9406(10)60511-1.
Testo completo
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Zhu, Zongxiao, Hui Wang, Zixuan Qiang, Shi Jiao, Linjun Wang, Min Zheng, Shengyu Zhu, Jun Cheng e Jun Yang. "Molecular Dynamics Study on Nano-Friction and Wear Mechanism of Nickel-Based Polycrystalline Superalloy Coating". Coatings 11, n. 8 (26 luglio 2021): 896. http://dx.doi.org/10.3390/coatings11080896.
Testo completoAbstract (sommario):
In this work, molecular dynamics simulations are employed to study the nanotribological process of nickel-based polycrystalline superalloy coating. A series of simulations were carried out using the method of repeated friction to explore the influence of frictional force, friction coefficient, grinding groove morphology, wear scar depth, debris flow direction, subsurface damage degree and evolution of defects during the nano-friction process. In addition, the change mechanism of different grain sizes on wear scar depth, frictional force, friction coefficient, and internal damage in the repeated friction process is also explored. The results show that the frictional force is related to the direction of the dislocation slip, and that the friction coefficient change is related to the number of repeated frictions. Moreover, it is observed that the grinding ball has a shunting effect on the formed wear debris atoms, and the shunt point is located at the maximum horizontal radius. We reveal that the grain boundary structure has a strengthening effect. When the grinding ball rubs to the grain boundary, the nucleation of dislocation defects inside the workpiece is obviously hindered by it. Simultaneously, we also find that the closer the subsurface is to the bottom of the grinding ball, the greater the degree of damage to the workpiece by friction. Furthermore, with the grain size decreases that the material begins to soften, resulting in a decrease of frictional force, friction coefficient, and smaller defects are formed inside the workpiece. The research of this work can better clarify the microscopic mechanism of the polycrystalline friction process.
3
Li, Jing-Ming, Hai-Jun Wei, Li-Dui Wei, Da-Ping Zhou e Ye Qiu. "Extraction of Frictional Vibration Features with Multifractal Detrended Fluctuation Analysis and Friction State Recognition". Symmetry 12, n. 2 (11 febbraio 2020): 272. http://dx.doi.org/10.3390/sym12020272.
Testo completoAbstract (sommario):
For the purpose of extracting the frictional vibration characteristics of the friction pair during friction and wear in different friction states, the friction and wear tests of friction pair in different friction states were conducted on a testing machine. Higher-dimensional fractal and multifractal characteristics hidden in time series can be examined by multifractal detrended fluctuation analysis (MFDFA) method. The frictional vibration time-domain signals, the friction coefficient signals and the frictional vibration frequency-domain signals were analyzed and multifractal spectra were acquired by using the MFDFA algorithm. According to the spectra, the multifractal spectrum parameters of these signals were calculated to realize the quantitative characterization of frictional vibration characteristics in different friction states. The analysis shows that it is symmetric in the variation trends of the multifractal spectrum parameters of the frictional vibration signals and the friction coefficient data. Based on the multifractal spectrum parameters of frictional vibration, the principal component analysis (PCA) algorithm was applied to establish the friction state recognition method. The results show that the multifractal spectra and their parameters can characterize the frictional vibrations, and the friction state recognition can be realized based on the multifractal spectrum parameters of frictional vibrations.
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Qiao, Yu Lin, Shan Lin Yang, Yan Zang e Xin Yu Dong. "Effects of Ultrasonic Vibration on Tribological Properties of GCr15/45# Steel Frictional Pairs in Lubricated Sliding Conditions under Various Friction Speed". Advanced Materials Research 338 (settembre 2011): 599–602. http://dx.doi.org/10.4028/www.scientific.net/amr.338.599.
Testo completoAbstract (sommario):
The effects of friction speed and ultrasonic vibration on friction reduction and anti-wear properties of GCr15/45# steel frictional pairs under oil lubrication were investigated by a modified MFT-R4000 reciprocating friction and wear tester. The mechanism of friction reduction and anti-wear under ultrasonic vibration was discussed. The results showed that, the ultrasonic vibration could influence the friction reduction and anti-wear properties of frictional pairs due to it could reduce the stress between the friction pairs and destroy the oil film on the surface of samples. When the friction frequency was 2Hz，ultrasonic vibration would reduce the friction coefficient and wear volume of the frictional pairs. When the load was 40N, the friction coefficient and wear volume of the frictional pairs attained under ultrasonic vibration decreased 8% and 44% respectively. However, ultrasonic vibration would increase the friction coefficient and wear volume when the friction frequency was 5Hz. When the load was 30N, friction coefficient and wear volume of frictional pairs increased 11% and 74% than that without ultrasonic vibration respectively.
5
Fang, Kun. "Frictional Performance of Polyphenyl Ester Modified Polytetrafluoroethylene". Materials Science Forum 1080 (30 gennaio 2023): 33–39. http://dx.doi.org/10.4028/p-g7gf9i.
Testo completoAbstract (sommario):
This paper mainly studied the coefficient of friction (COF), wear performance and frictional vibration performance of polyphenyl ester modified polytetrafluoroethylene under dry friction and water lubrication friction conditions. Polyphenyl ester modified polytetrafluoroethylene composites were prepared by blending 20% polyphenyl ester with polytetrafluoroethylene, and the COF, wear performance and frictional vibration properties of such composites were tested. The results showed that: (1) Under dry friction conditions, as the specific pressure between the friction pairs increased, the volume of wear and the thickness of the wear increased, the COF decreased at first and then increased, the frictional vibration increased and stabilized after the pressure of 0.5 MPa. (2) Under water-lubricated friction conditions, as the specific pressure between the friction pairs increased, the COF increased, and the frictional vibration increased and stabilized after the pressure of 0.5 MPa; (3) The wear resistance of polyphenyl ester modified polytetrafluoroethylene composite under water-lubricated friction was better than that under dry friction, the COF was less than that under dry friction, and the total level of frictional vibration was slightly lower than that under dry friction. Therefore, in order to reduce frictional vibration and improve service life, the working pressure should be reduced, and the lubrication performance between the friction surfaces should be improved. Under water-lubricated friction, the maximum working pressure of the polyphenyl ester modified polytetrafluoroethylene composite system is recommended not to exceed 0.8 MPa.
6
Wang, Tian Guo, X. Y. Liu e J. J. Hua. "Investigation on the Fabrication and Properties of the Cu Base Friction Composites". Materials Science Forum 984 (aprile 2020): 125–30. http://dx.doi.org/10.4028/www.scientific.net/msf.984.125.
Testo completoAbstract (sommario):
Cu-based friction materials were prepared by powder metallurgy technology. The effect of Fe content on friction and wear properties of Cu-based friction materials has been investigated. The results indicate that Fe content has great effects on the wear ability of Cu-based friction materials. Fe works as frictional component in copper-based friction materials, influening the mechanical and frictional property of materials. With increasing Fe content, the hardness and friction coefficient of Cu-based friction materials stability increase, the wear rate of the friction materials decreases. When Fe content is 6%, the materials posses stably high friction factors, as well as good wear ability.
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Zhang, Zijian, Guangwu Zhou, Peng Li, Luole Du e Min He. "Research on the Vibration Behavior of Ring–Block Friction Pair Made of Materials of Water-Lubricated Rubber Bearing under Special Operating Conditions". Applied Sciences 13, n. 13 (28 giugno 2023): 7676. http://dx.doi.org/10.3390/app13137676.
Testo completoAbstract (sommario):
A water-lubricated rubber bearing (WLRB) is prone to generate frictional vibration noise under special operating conditions, which seriously affects the acoustic stealth performance of warships and threatens their navigation safety. Meanwhile, the main factor affecting the frictional vibration behavior of a WLRB is the materials of the friction pair. Therefore, this work selects a friction pair composed of a copper ring and a rubber block as the research object and studies the frictional vibration behavior of the ring–block friction pair under low-speed and starting conditions. The real friction coefficient curve is used to establish a transient dynamic finite element analysis model for the ring–block friction pair. The effects of the load, friction coefficient, and Young’s modulus on the frictional vibration behavior under special operating conditions are studied. The analysis’s results show that the frequency of the medium-high frequency friction-induced vibration disappears under low-speed operating conditions when the friction coefficient is below 0.1. During the startup process, even if the friction coefficient is very low, the medium-high frequency friction-induced vibration still exists. The research results provide ideas for future theoretical research and guidance suggestions for engineering practice.
8
Fang, Shanglong, Wei Xiao, Kewen Chen e Xuding Song. "Research on the Model for the Friction Coefficient of Resin-Based Friction Material and Its Experimental Verification". Materials 16, n. 13 (3 luglio 2023): 4791. http://dx.doi.org/10.3390/ma16134791.
Testo completoAbstract (sommario):
Resin-based friction materials have been widely used in the friction braking of automobiles and power machinery. Based on experiments for the variation law of friction and wear morphology, a new model for the friction coefficient of resin-based friction materials was proposed, which includes the effects of both the micro convex body on the surface of the friction material and the frictional film generated during the friction process. This quantitative model of friction coefficient materials was established for the modelling of shear strength, compressive strength, shear strength of the frictional film, contact load and wear morphology. The shear strength, compressive strength and wear morphology of the friction material were adjusted by changing the content of basalt fibers and flaky potassium magnesium titanate. Finally, the accuracy of this quantitative model of friction coefficient was verified through experiments on friction samples with different formulations and by changing the frictional contact load. The results show that the predicted friction coefficient of the model is in good agreement with the experimental friction coefficient, the difference between the upper and lower limits of the forecast is only 5.03% and 2.30%, respectively. Meanwhile, the influence of the ratio of shear strength to compressive strength on the friction coefficient is greater than the proportion of wear morphology. The proposed friction model provides a reference value for the study of new resin-based friction materials.
9
Bates, Jo. "The politics of data friction". Journal of Documentation 74, n. 2 (12 marzo 2018): 412–29. http://dx.doi.org/10.1108/jd-05-2017-0080.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is twofold: first, to further develop Paul Edwards’ concept of “data friction” by examining the socio-material forces that are shaping data movements in the cases of research data and online communications data, second, to articulate a politics of data friction, identifying the interrelated infrastructural, socio-cultural and regulatory dynamics of data friction, and how these are contributing to the constitution of social relations. Design/methodology/approach The paper develops a hermeneutic review of the literature on socio-material factors influencing the movement of digital data between social actors in the cases of research data sharing and online communications data. Parallels between the two cases are identified and used to further develop understanding of the politics of “data friction” beyond the concept’s current usage within the Science Studies literature. Findings A number of overarching parallels are identified relating to the ways in which new data flows and the frictions that shape them bring social actors into new forms of relation with one another, the platformisation of infrastructures for data circulation, and state action to influence the dynamics of data movement. Moments and sites of “data friction” are identified as deeply political – resulting from the collective decisions of human actors who experience significantly different levels of empowerment with regard to shaping the overall outcome. Research limitations/implications The paper further develops Paul Edwards’ concept of “data friction” beyond its current application in Science Studies. Analysis of the broader dynamics of data friction across different cases identifies a number of parallels that require further empirical examination and theorisation. Practical implications The observation that sites of data friction are deeply political has significant implications for all engaged in the practice and management of digital data production, circulation and use. Social implications It is argued that the concept of “data friction” can help social actors identify, examine and act upon some of the complex socio-material dynamics shaping emergent data movements across a variety of domains, and inform deliberation at all levels – from everyday practice to international regulation – about how such frictions can be collectively shaped towards the creation of more equitable and just societies. Originality/value The paper makes an original contribution to the literature on friction in the dynamics of digital data movement, arguing that in many cases data friction may be something to enable and foster, rather than overcome. It also brings together literature from diverse disciplinary fields to examine these frictional dynamics within two cases that have not previously been examined in relation to one another.
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Jang, Siyoul. "Manipulating Frictional Performance of Wet Clutch Engagement through Material Properties and Operating Conditions". Lubricants 10, n. 9 (19 settembre 2022): 225. http://dx.doi.org/10.3390/lubricants10090225.
Testo completoAbstract (sommario):
Wet clutch engagement is mainly influenced by the frictional behaviors between the friction pad and steel plate as well as the lubrication behaviors. A positive μ–V friction coefficient of the wet clutch pad is the most preferable characteristic for improving antishudder behavior. In this study, a wet clutch engagement mechanism is theoretically divided into two major frictional behaviors, namely, direct asperity contact of interacting surfaces and hydrodynamic lubrication, for positive μ–V friction performance. These two behaviors are investigated with regard to both material characteristics of the friction pad–steel plate interactions and hydrodynamic lubrication mechanism. Frictional interactions of the friction pad are analyzed according to the material properties of the friction pad, such as elasticity, permeability, and roughness. Hydrodynamic lubrication, by which the initial period of the engagement is dominantly governed by the waviness of surface shape, is investigated to increase the frictional resistance in the initial stage of engagement relative to that in the final stage of engagement for realizing a positive μ–V friction coefficient. Computational simulations of wet clutch engagement behaviors are performed and compared with each other to obtain positive μ–V friction characteristics of the friction pad.
11
Dong, Xin Yu, Yu Lin Qiao, Yan Zang e Qing Sheng Cui. "Effects of Friction Load and Ultrasonic Vibration on the Tribological Properties of Al2O3/Al2O3 Ceramic Friction Pairs under Liquid Paraffin Lubrication". Advanced Materials Research 652-654 (gennaio 2013): 1881–85. http://dx.doi.org/10.4028/www.scientific.net/amr.652-654.1881.
Testo completoAbstract (sommario):
The effects of friction load and ultrasonic vibration on friction reduction and anti-wear properties of Al2O3/Al2O3 ceramic frictional pairs under oil lubrication were investigated by a modified MFT-R4000 reciprocating friction and wear tester. The mechanism of friction reduction and anti-wear under ultrasonic vibration was discussed. The results showed that, the ultrasonic vibration could influence the friction reduction and anti-wear properties of Al2O3/Al2O3 ceramic friction pairs due to it could reduce the stress between the friction pairs and destroy the oil film on the surface of samples. When the friction frequency was 2Hz, the ultrasonic vibration could reduce the friction coefficient within experiment load range. When the loads were 70N, 80N, 90N and 100N, the average friction coefficient were reduced by 16.1%, 14.5%, 9.7% and 2.6%,and wear volume of frictional pairs decreased 35%、32%、31% and 12%.
12
Manandhar, Suman, Noriyuki Yasufuku, Kiyoshi Omine e Taizo Kobayashi. "Response of tapered piles in cohesionless soil based on model tests". Journal of Nepal Geological Society 40 (1 dicembre 2010): 85–92. http://dx.doi.org/10.3126/jngs.v40i0.23613.
Testo completoAbstract (sommario):
This paper describes model tests of different types of tapered piles in cohesionless soils. Chromium plated three steel piles, one straight and two taper-shaped piles of same length and pile tip diameters have been executed for pile loading test in a downward frictional mode. Two different types of model grounds have been prepared for the test. Relative densities of 80 % and 60 % have been modeled to penetrate piles in two different types of sands to observe the effectiveness of skin frictions of different types of piles. The response of tapered piles has shown that the skin friction has increased with increasing the tapering angle at normalized settlement ratio of 0.4. High density ground yields higher skin friction when the maximum tapered pile was penetrated. Slightly increased tapering angle of the pile affects remarkably on the skin friction with compared to conventional straight cylindrical pile even at small 0.1 settlement ratios.
13
Krykhtin, Yu I., e V. I. Karlov. "HIGH-PERFORMANCE METHOD OF PRODUCTION OF POWDER FRICTIONAL PRODUCTS ON FE-BASIS WITH HIGH TECHNOLOGICAL AND OPERATIONAL PROPERTIES". IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, n. 2(249) (25 febbraio 2021): 20–26. http://dx.doi.org/10.35211/1990-5297-2021-2-249-20-26.
Testo completoAbstract (sommario):
Physical and technological bases of DHP-PFM method for production of dry friction powder friction articles on Fe-base with high technological and operational indices for a wide range of practical use have been developed. The DHP-PFM method is that the dynamic hot pressing (DHP) provides production of the new powder frictional materials (PFM) through an underlayer from carbonyl iron between frictional material and a basis (framework) with electroplated nickel coating. Friction lining compaction is made of charge of ФМК-79 type and has high hardness and low porosity. Processes of the choice of composition of furnace charge, formation of structure and properties of new powder frictional materials on Fe-to a basis are investigated. The method is characterized by high productivity, energy saving, simplified technology and provides the possibility to use existing technological equipment for making structural powder products. Method of DHP-PFM manufacturing of dry friction powder friction linings can be used for manufacturing of friction units of transmissions of light track machines with high specific power. The friction material received by this method from furnace charge of FMK-79 type can be used as unified for such frictional units as the main friction clutch, an onboard friction clutch, tape and disk brakes.
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Luo, Shenq Yih, e Can Yu Bai. "Study of Metal Friction Materials Using Hot Press". Advanced Materials Research 750-752 (agosto 2013): 2084–87. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.2084.
Testo completoAbstract (sommario):
The metal friction materials of copper matrix with and without resin using hot press were investigated to study their hardness, porosities, bending strengths, microstructures, coefficient of frictions, and wear mechanisms. The experiment results show that the hardness and bending strength of the friction materials with increase of amount of copper increase, but the porosity decreases. The resulting coefficient of frictions show more stable and their values are about 0.5~0.6. In addition, the wear mechanism of friction material shows mainly grit abrasive and adhesion, which cause the coefficient of friction to become stable. On the other hand, when the copper matrix containing resin is used, the resulting porosity of friction materials becomes higher and the bending strength decreases. This shows that the wear mechanisms of grit abrasive, roughness, and adhesion cause the coefficient of friction to produce a higher value.
15
Ahagon, Asahiro, Toshio Kobayashi e Makoto Mlsawa. "Friction on Ice". Rubber Chemistry and Technology 61, n. 1 (1 marzo 1988): 14–35. http://dx.doi.org/10.5254/1.3536173.
Testo completoAbstract (sommario):
Abstract The friction on ice is strongly dependent on temperature. At sufficiently low temperatures, the frictional resistance on ice is high comparable to those on wet or even dry solid surfaces. As temperature rises and approaches the melting point of ice, however, friction rapidly decreases. Differing from the friction of a rubber on ordinary dry or wet solid surfaces the energy loss processes in the rubber do not seem to be the direct source of the frictional resistance on ice. Although frictional melting of ice could occur at high sliding speeds, an ice surface is inherently lubricated with a persistent mobile fluid layer at relatively high temperatures, near the melting point of ice. When a rubber slides on an ice surface, the fluid layer is sheared and undergoes drag flow. The energy loss process necessary for the frictional resistance takes place primarily in the fluid layer, and not in the rubber. The frictional resistance on ice is primarily determined by the viscosity and the thickness of the lubricating fluid layer. What is required of a rubber for better traction under such a condition is that the rubber surface follows the topography of the ice surface as closely as possible, so that more patches of ice surface can be sheared. Therefore, the rubber has to be sufficiently soft to show high friction on ice. Further improvement of the friction could be obtained by making it more resilient. Thus, a rubber with high friction on ice must be compounded so that the polymer chains maintain a high level of mobility at moderately low temperatures. This can be achieved by using polymers with low glass-transition-temperatures. An increased softener loading level helps to improve friction, but to a limited extent. In order to take maximum advantage of softeners, the choice of softener system is important. A relation common to all the mixed softener systems, except the ones containing high-viscosity softeners, was found to exist between the friction on ice and the solubility parameter of the softener mixture in the rubber. The friction on ice was maximized by selecting a softener system with a solubility parameter near that of the polymers in the rubber. The solubility parameter dependence of the friction was consistent with those of softness and resilience.
16
Hosseinali, Farzad, e J. Thomasson. "Multiscale Frictional Properties of Cotton Fibers: A Review". Fibers 6, n. 3 (13 luglio 2018): 49. http://dx.doi.org/10.3390/fib6030049.
Testo completoAbstract (sommario):
This review discusses the important concept of cotton fiber friction at both the macro- and nanoscale. First, the technological importance of fiber friction and its role in fiber breakage during fiber processing is discussed. Next, previous studies on frictional properties of cotton fibers are reviewed and different experimental procedures to measure friction between fibers or against another surface are evaluated. Friction models developed to explain friction process during various experimental procedures are considered and their limitations are discussed. Since interpretation of friction processes at the macroscale can be challenging (mainly due to difficulties in analyzing the multiple asperities in contact), a separate section is devoted to surveying studies on the emerging field of single-asperity friction experiments with atomic force microscope (AFM). Special attention is given to studies on nanoscale frictional characteristics of rough viscoelastic surfaces (e.g., plant cuticular biopolymers and cotton fibers). Due to the close relationship between friction and adhesion hysteresis at the nanoscale, adhesion studies with AFM on viscoelastic surfaces are also reviewed. Lastly, recommendations are made for future research in the field of frictional properties of cotton fibers.
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Zhang, Zhigang, Ling Zou, Hang Liu, Yonglong Chen e Benzhu Zhang. "Effects of operating and material parameters on the thermal characteristics of a wet clutch". Advances in Mechanical Engineering 13, n. 7 (luglio 2021): 168781402110341. http://dx.doi.org/10.1177/16878140211034101.
Testo completoAbstract (sommario):
Based on the frictional mechanism of a wet clutch, frictional models of wet clutch engagement were established using the modified Reynolds equation and the elastic contact model between frictional pairs. Then, the heat flux models for the viscous shear and asperity friction were built, and the two-dimensional transient thermal models for the separator plate, friction disk, and ATF heat convection model were deduced based on the heat transfer theory and conservation law of energy. Finally, the Runge–Kutta numerical method was used to solve the frictional and thermal models. The average temperature of the separator plate, friction disk, and ATF were calculated. The effects of operating and material parameters, such as applied pressure, initial angular velocity, friction lining permeability, surface combined roughness RMS, equivalent elastic modulus, and ATF flow, on the thermal characteristics of friction pairs and ATF during engagement, were studied. The simulation results show that the temperature characteristics of the separator plate, friction disk, and ATF depend mainly on the viscous shear and asperity friction heat flux, and that the operating and material parameters of the wet clutch also have significant impacts on the overall variation trend of the thermal characteristics of the separator plate, friction disk, and ATF.
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Al-Karkhi, Nazar, Nadica Stojanovic, Salah Al-Zubaidi, Muhsin Jaber Jweeg, Hakim S. Sultan, Azher M. Abed e Oday I. Abdullah. "Experimental Investigation of Thermal Effect on the Frictional Characteristics of HCC Friction Clutch Material". Tribology in Industry 46, n. 1 (marzo 2024): 141–50. http://dx.doi.org/10.24874/ti.1465.03.23.12.
Testo completoAbstract (sommario):
Increasing temperature due to frictional heat from sliding between contacting surfaces leads to increased wear and friction. Therefore, the researchers continue investigations to find the most suitable friction materials with good mechanical and thermal properties for frictional facings of clutch performance under this condition. In this research paper, the behavior and performance of the friction material HCC was studied under different normal load conditions (125, 175, 225, and 275 N) and different working environment temperatures (300 K and 390 K), where the rotation speed was 300 rpm. The results of the coefficient of friction and friction forces variation under different working conditions were analyzed and discussed in detail. XTM 500 tribometer test rig was used to perform the required tests, and the samples were made of the HCC friction material. The obtained results proved that the ambient temperature of the friction system has a significant negative effect on both the coefficient of friction and the force of friction. So, when the friction system's ambient temperature increases, the magnitude of the friction coefficient will decrease, and, thus, the transmitted torque will reduce too.
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Rajapakshe, M. P., M. Gunaratne e A. K. Kaw. "Evaluation of LuGre Tire Friction Model with Measured Data on Multiple Pavement Surfaces". Tire Science and Technology 38, n. 3 (1 settembre 2010): 213–27. http://dx.doi.org/10.2346/1.3481671.
Testo completoAbstract (sommario):
Abstract Accurate modeling of tire/pavement friction phenomena is of utmost importance in many applications such as vehicle braking control and frictional evaluation of pavements. LuGre tire friction model is a model which is used for this purpose by estimating its parameters using measured pavement friction data. In this investigation, LuGre model parameters were estimated using field data collected by a standard pavement friction measuring device (Locked Wheel Skid Trailer-ASTM E 274) at a group of pavements with different surface friction properties. Adequacy of the model to predict measured friction data from the device was statistically evaluated and the accuracy of estimated model parameters was determined. The results show the potential of this model to facilitate frictional evaluation of pavements using dynamic friction measuring equipment.
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Wu, Xiangyu, e Yanzhong Wang. "Experimental investigations of tribological performances of novel friction pair with different conical configurations". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, n. 8 (28 febbraio 2019): 1245–55. http://dx.doi.org/10.1177/1350650119834424.
Testo completoAbstract (sommario):
Friction plate with conical configuration is a novel application in automatic transmission. In order to investigate the tribological performances of novel friction pair with different conical configurations, a series of tests are conducted by using a variable-speed friction test rig. The lubrication regime is evaluated by the friction coefficient curves under different loads. Test results of the friction coefficient under different rotating speeds are analyzed. The difference in the frictional behavior is analyzed for different conical friction pairs. The effects of the cone height and cone angle are evaluated under the same dimensions. Results show that changes in the conical configuration indeed influence the frictional behaviors of the friction specimens. Rational determination of the conical configuration is helpful to obtain good tribological performance.
21
Qiao, Yu Lin, Shan Lin Yang, Yan Zang e Dong Wang. "Effect of Ultrasonic Vibration on Friction and Wear Properties of GCr15/45# Steel Frictional Pairs under Oil Lubrication". Advanced Materials Research 295-297 (luglio 2011): 2102–5. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.2102.
Testo completoAbstract (sommario):
Ultrasonic vibration friction and wear experiments were carried out by MFT-R4000 reciprocating friction and wear tester bonded with ultrasonic device. The surface morphologies of wear scars were examined by scanning electron microscope (SEM). The influences of ultrasonic vibration on friction reduction and anti-wear properties of GCr15/45# steel frictional pairs under different loads were discussed. The experimental results showed that, the friction of GCr15/45# steel frictional pairs could be reduced by ultrasonic vibration, and the reduction of friction coefficient became more obvious as the loads increasing. The friction coefficient measured under ultrasonic vibration is 12% lower than it measured without ultrasonic vibration when the load was 50N. However, the wear of frictional pairs increased under ultrasonic vibration, and the amplitude of wear volume enlarged with the loads increase, which is 63% at the load of 50N.
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Alhasan, Ahmad, Omar Smadi, Georges Bou-Saab, Nacu Hernandez e Eric Cochran. "Pavement Friction Modeling using Texture Measurements and Pendulum Skid Tester". Transportation Research Record: Journal of the Transportation Research Board 2672, n. 40 (30 maggio 2018): 440–51. http://dx.doi.org/10.1177/0361198118774165.
Testo completoAbstract (sommario):
Pavement frictional behavior affects pavement performance in terms of vehicle safety, fuel consumption, and tire wear. Comprehending and interpreting pavement friction measurements is a challenging task, because of friction sensitivity to several uncontrollable factors. These factors include: pavement surface conditions, such as the type and thickness of contaminants and fluids on the surface and their interaction with friction forces; and the device operating conditions, such as sliding speed, material properties and geometry of the rubber slider used, and operating temperature. Despite the efforts to describe and quantify the impact of varying conditions on pavement friction, which ultimately will allow for a better harmonization of friction measurements, there is a need to better understand the link between the surface texture and physical friction measurements. In this paper, Persson’s friction model is used to analyze and understand the impact of surface texture on frictional behavior of dry pavement surfaces. The model was used to analyze 18 test locations, which were compared with the dry kinetic coefficients of friction (COF) estimated using a British pendulum tester (BPT). The results show that Persson’s friction model could predict the COF estimated from the BPT results with relatively high accuracy. In addition, the model could provide a profound explanation of the frictional forces mechanism. Finally, it was found that the mean profile depth (MPD) cannot provide a full picture of the frictional behavior. However, combining MPD with the Hurst exponent, texture measurements can potentially provide a full physical explanation of the frictional behavior for road surfaces.
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OLEKSOWICZ, SELIM, e ANDRZEJ MRUK. "FRICTION PROCESS IN THE PRESENCE OF HARD ABRASIVE PARTICLES — COOPERATION MODEL". Surface Review and Letters 18, n. 06 (dicembre 2011): 249–59. http://dx.doi.org/10.1142/s0218625x11014734.
Testo completoAbstract (sommario):
The paper presents the results of the investigation performed on a stand for model testing of the friction pair like a car disc brake. The tests were performed for the mating operation of a frictional node with the dosage of hard abrasive particles into the friction zone. Based on the observation of the phenomena in the friction zone and the analysis of the parameters describing operating conditions of a frictional node, physical models of the frictional node cooperation in the presence of hard abrasive particles have been proposed. During the tests, using the transparent material of a friction cover plate and a fast recording camera, a visual analysis of the material transfer in the friction zone was done. It allowed to positively verifying the proposed physical models of the frictional node cooperation in the presence of hard abrasive particles.
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Kong, Hai-Yan, e Ji-Huan He. "A novel friction law". Thermal Science 16, n. 5 (2012): 1529–33. http://dx.doi.org/10.2298/tsci1205529k.
Testo completoAbstract (sommario):
Frictional force is a vitally important factor in the application of engineering either in macroscopic contacts or in micro/nanoscale contacts. Understanding of the influencing factors about frictional force is essential for the design of miniaturized devices and the use of minimal friction force. In the paper, dimensional analysis is used to analysis factors relative to frictional force. We show that the frictional force scales with where A is the contact area and N is the normal contact force. An experiment is carried out to verify the new friction law.
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Zhang, Lijun, Wenbo Li e Dejian Meng. "Influence of Heterogeneous Contact Stiffness and Heterogeneous Friction Coefficient on Frictional Squeal". Shock and Vibration 2018 (2018): 1–21. http://dx.doi.org/10.1155/2018/6379201.
Testo completoAbstract (sommario):
Contact stiffness and friction coefficient are excitation sources and key influencing factors to frictional squeal with obvious inhomogeneous characteristic that is always neglected. In this paper, a multipoint contact flexible pin-on-disc system is established considering tangential stiffness. Then influence of contact stiffness and friction coefficient with heterogeneous distribution on frictional squeal is studied using the complex modal analysis. The research shows that contact stiffness and friction coefficient heterogeneities influence the likelihood of occurrence of the squeal, the frequency of the squeal, and the real part of the complex eigenvalue of the system. And when the contact stiffness and friction coefficient are close to the boundary of the region of mode-coupling instability, flexible pin-on-disc system with homogeneous contact stiffness and friction coefficient cannot predict whether frictional squeal occurs or not. Besides, uncertain distribution of contact stiffness and friction coefficient can induce the uncertainty of brake squeal.
26
Hou, Jun Tao, Sheng Ru Qiao, Guo Feng Lu, Cheng Yu Zhang e Yue Bing Zhang. "Internal Friction of a 2D-C/SiC Composite from 25°C to 400°C". Key Engineering Materials 353-358 (settembre 2007): 1509–12. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1509.
Testo completoAbstract (sommario):
By means of forced non-resonance under 3-point bending method, the internal frictions of 2D-C/SiC composites are carried out from 25°C to 400°C in air. The effects of temperature, amplitude and frequency on internal frictions have been analyzed. Results show that interface layer plays a dominant role to internal friction. When temperature increases from 25°C to 400°C, internal friction of 2D-C/SiC composite increases slightly, and storage modulus decreases monotonically. With frequency increases from 1Hz to 100Hz, internal friction reduces to a minimum around 10Hz, whereas above 50Hz it arises sharply. In amplitude scale from 0.5μm to 10μm, internal friction increases linearly with the increase of amplitude.
27
Tiwari, Ashish. "The Role of Friction in Athletic Performance: A Descriptive Analysis". INTERANTIONAL JOURNAL OF SCIENTIFIC RESEARCH IN ENGINEERING AND MANAGEMENT 08, n. 04 (28 aprile 2024): 1–5. http://dx.doi.org/10.55041/ijsrem31958.
Testo completoAbstract (sommario):
Friction is a fundamental force that has a substantial impact on athletic performance across all sports disciplines. This descriptive research investigates the varied impact of friction in building athletic skill. This study looks at how friction affects running, jumping, throwing, and other sports activities by examining static and kinetic frictional forces, as well as elements that influence frictional interactions. The research examines the interaction of athletes, footwear, surfaces, and equipment to explain how friction governs propulsion, stability, and efficiency in sports activity. The findings of this study have important significance for players, coaches, and sports scientists, as they provide avenues for optimizing training techniques, equipment design, and performance tactics for increased athletic achievement. Keywords Friction , Athletic Performance , Role , Descriptive Analysis , Surface Friction , Footwear Friction , Sports Science , Biomechanics , Performance Optimization , Surface Interaction , Traction , Stability , Movement Efficiency , Injury Prevention ,Training Strategies
28
Wei, Zhiyong, Li Xiang, Yajing Kan, Yan Zhang e Yunfei Chen. "Effects of the normal load on the excited phonons in atomic friction". Journal of Applied Physics 132, n. 17 (7 novembre 2022): 175301. http://dx.doi.org/10.1063/5.0113738.
Testo completoAbstract (sommario):
Although the quantitative relationship between the normal load and the induced friction force has been established from the phenomenological laws of friction, it does not answer the question of how mechanical energy is dissipated into heat by exciting phonons. In this study, the effects of normal load on the friction force of a relatively sliding graphene film are investigated by molecular dynamics simulations. The results show that the excited phonon modes couple with the resonant frequency of the entire frictional system, and the enhancement of the normal load is equivalent to the increase of the resonant frequency of the frictional system. It is also found that the relative intensity of the resonant peaks in the vibrational density of states is a key factor affecting the friction force, which can explain the variation of friction force with the normal load. Moreover, under a certain normal load, the friction force can reach its maximum value when the washboard frequency equals the resonant frequency of the frictional system. Our work establishes the relationship between the normal load and the frictional force from the phonon level, which provides a method for regulating atomic friction and energy dissipation by considering both washboard frequency and contact resonant frequency.
29
Zhao, Xue Zeng, Xi Gui Wang e Yong Mei Wang. "Analysis on the Influence of the Strength and Stiffness under the Contact Conditions for Friction Plate". Key Engineering Materials 579-580 (settembre 2013): 523–29. http://dx.doi.org/10.4028/www.scientific.net/kem.579-580.523.
Testo completoAbstract (sommario):
This paper mainly consider the friction plate finite element modeling frictional contact conditions between the slices of components, friction plate assembly of the strength and stiffness of the. Through modal analysis of force and its distribution in different layers of friction plate assembly friction plate, a friction plate component analysis layers, friction plate by the effect of preload on the friction plate assembly strength, and in this state analysis of the friction plate stiffness. On the contact state under different friction plate layers, different pre tightening force under stress, stiffness were compared, the effect of contact on the stiffness and friction plate component strength.
30
Trzepiecinski, Kubit, Slota e Fejkiel. "An Experimental Study of the Frictional Properties of Steel Sheets Using the Drawbead Simulator Test". Materials 12, n. 24 (4 dicembre 2019): 4037. http://dx.doi.org/10.3390/ma12244037.
Testo completoAbstract (sommario):
This article presents the results of an experimental investigation of the frictional resistance arising in a drawbead during sheet metal forming. The frictional characterization of DC04 deep drawing quality steels commonly used in the automotive industry is carried out using a friction simulator. The effects of some parameters of the friction process on the value of the coefficient of friction have been considered in the experimental investigations. The friction tests have been conducted on different strip specimens, lubrication conditions, heights of drawbead and specimen orientations in relation to the sheet rolling direction. The results of drawbead simulator tests demonstrate the relationship that the value of the coefficient of friction of the test sheets without lubrication is higher than in the case of lubricated sheets. The lubricant reduces the coefficient of friction, but the effectiveness of its reduction depends on the drawbead height and lubrication conditions. Moreover, the effectiveness of the reduction of the coefficient of friction by the lubricant depends on the specimen orientation according to the sheet rolling direction. In the drawbead test, the specimens oriented along the rolling direction demonstrate a higher value of coefficient of friction when compared to the samples cut transverse to the rolling direction. The smaller the width of the specimen, the lower the coefficient of friction observed. The difference in the coefficient of friction for the extreme values of the widths of the specimens was about 0.03–0.05. The use of machine oil reduced the coefficient of friction by 0.02–0.03 over the whole range of drawbead heights. Heavy duty lubricant even reduced the frictional resistances by over 50% compared to dry friction conditions. The effectiveness of friction reduction by machine oil does not exceed 30%.
31
Kobzev, Kirill, Yuliya Goncharova e Nataliya Kobzeva. "The process of increasing the stable operation of the working body in crank presses". E3S Web of Conferences 164 (2020): 03017. http://dx.doi.org/10.1051/e3sconf/202016403017.
Testo completoAbstract (sommario):
The article considers the study of the synthesized concept of frictional contact of solids in crank presses. As a result of the analysis the possibility of obtaining the maximum load characteristic of the friction contact within the interval of variation of the friction coefficient has been established. The possibility of equality of the values of the friction force of the friction contact at the boundaries of the indicated interval in the presence of a maximum and the achievement of their greatest stability under these conditions is also revealed. As result the upgraded concept of frictional contact allows theoretically to obtain a very high stability of the friction force, however, due to the relatively large value of the angle and force parameter, it is used inefficiently. A necessary condition for the absence of zero reversal of the output parameter of the main friction group of the friction contact in the interval of variation of the friction coefficient and the presence of the maximum function of the load capacity of the friction contact is the transfer of its full load by the sensitive elements of the additional friction group. An additional condition for the existence of a maximum is the need for the sensitive elements of the main friction group to transfer part of its full load at an equal number of friction pairs of both friction groups, and for the sensitive elements to transfer the full load of the main friction group at a lower number of friction pairs than in the additional friction group.
32
Li, Qunyang, e Kyung-Suk Kim. "Micromechanics of friction: effects of nanometre-scale roughness". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 464, n. 2093 (19 febbraio 2008): 1319–43. http://dx.doi.org/10.1098/rspa.2007.0364.
Testo completoAbstract (sommario):
Nanometre-scale roughness on a solid surface has significant effects on friction, since intersurface forces operate predominantly within a nanometre-scale gap distance in frictional contact. To study the effects of nanometre-scale roughness, two novel atomic force microscope friction experiments were conducted, each using a gold surface sliding against a flat mica surface as the representative friction system. In one of the experiments, a pillar-shaped single nano-asperity of gold was used to measure the molecular-level frictional behaviour. The adhesive friction stress was measured to be 264 MPa and the molecular friction factor 0.0108 for a direct gold–mica contact. The nano-asperity was flattened in contact, although its hardness at this length scale is estimated to be 3.68 GPa. It was found that such a high pressure could be reached with the help of condensed water capillary forces. In the second experiment, a micrometre-scale asperity with nanometre-scale roughness exhibited a single-asperity-like response of friction. However, the apparent frictional stress, 40.5 MPa, fell well below the Hurtado–Kim model prediction of 208–245 MPa. In addition, the multiple nano-asperities were flattened during the frictional process, exhibiting load- and slip-history-dependent frictional behaviour.
33
Shishkarev, M. P., e Tien Dung Vu. "Determination of parameters of adaptive friction clutches with single-loop negative feedback". Traktory i sel hozmashiny 81, n. 8 (15 agosto 2014): 32–36. http://dx.doi.org/10.17816/0321-4443-65551.
Testo completoAbstract (sommario):
Dependencies of amplification coefficient on frictional coefficient are obtained for adaptive friction clutches with differentiated friction couples and with all leading friction couples. These dependencies allow to exclude theoretically influence of frictional coefficient changes on stability of transmitted load. It is shown that high stability of transmitted load can be achieved only in case of clutches with greater numbers of disks.
34
Luo, Xiao Yan, e Wei Ping Liu. "Analysis of Ultralong Friction Pile Based on Gradient Dependent Nonlocal Friction Model". Applied Mechanics and Materials 638-640 (settembre 2014): 380–83. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.380.
Testo completoAbstract (sommario):
Based on the gradient theory, the gradient dependent nonlocal friction model is established. It is a new model which can describe the nonlocal friction effect. Based on Mindlin’s solution of displacement, an elastic solution of the lateral frictional resistance for ultralong friction pile is derived. The ultralong friction pile is analyzed by using the gradient dependent nonlocal friction model. Compared with the solution to the local friction law, the results shows that nonlocal friction law is feasible and reliable. The study is helpful for understanding the friction mechanism in geotechnical problems. It is a good attempt to set up the more actual and more accurate friction model.
35
Bai, Shaoxian, Tao Wang e Jing Yang. "An Experiment on the Dwell Time Effect of Rubber Seal O-Rings: Friction Force in Intermittent Reciprocating Motion". Materials 17, n. 10 (17 maggio 2024): 2427. http://dx.doi.org/10.3390/ma17102427.
Testo completoAbstract (sommario):
The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring's rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.
36
Jaramillo-Vallejo, Pedro María, e Olga Bibiana Salcedo-Ospina. "Friction in orthodontics". Revista Facultad de Odontología 35, n. 2 (4 dicembre 2023): 77–96. http://dx.doi.org/10.17533/udea.rfo.v35n2a8.
Testo completoAbstract (sommario):
Friction is a fundamental aspect of orthodontic movement. Researchers and clinicians must be acquainted with its biomechanical and physical principles, as well as the potential alterations that may occur with the use of diverse materials. This literature review presents an approach of the physical principles at work in frictional mechanics, an analysis of the friction, at macro and microscopic level, of different orthodontic materials; describes the influence of friction on tooth movement and presents an update on friction research and its relationship to various materials.
37
Mamatha, B., Mohammed Nashiroddin, Lalitha Ch, Srinivas Kumar, Venkata Naidu e Sumayya Fatima. "Frictional Resistance in Orthodontics -A Review". South Asian Research Journal of Oral and Dental Sciences 4, n. 2 (26 maggio 2022): 10–14. http://dx.doi.org/10.36346/sarjods.2022.v04i02.002.
Testo completoAbstract (sommario):
This article reviews the frictional resistance of archwires based on the cross section, microscopic structure and stiffness. Bracket factors like slot width and depth and material influencing friction. Different types of ligation influencing friction. Role of saliva, biofilm and wire bracket combinations on friction. Friction in wire, bracket and ligation combination.
38
Tecco, Simona, Stefano Tetè e Felice Festa. "Friction between Archwires of Different Sizes, Cross-Section and Alloy and Brackets Ligated with Low-Friction or Conventional Ligatures". Angle Orthodontist 79, n. 1 (1 gennaio 2009): 111–16. http://dx.doi.org/10.2319/101107-487.1.
Testo completoAbstract (sommario):
Abstract Objective: To test the null hypothesis that no statistically significant difference in frictional resistance is noted when round or rectangular archwires are used in conjunction with low-friction ligatures (small, medium, or large) or conventional ligatures. Materials and Methods: A total of 10 stainless steel brackets, a 0.022-in slot, and various orthodontic archwires, ligated with low-friction ligatures or conventional ligatures, were tested to compare frictional resistance. The archwires employed were 0.014-in and 0.016-in nickel titanium (NiTi), 0.018-in stainless steel (SS), 0.016 × 0.022-in NiTi, 0.016 × 0.022-in SS, 0.017 × 0.025-in titanium molybdenum alloy (TMA), 0.017 × 0.025-in NiTi, 0.017 × 0.025-in SS, 0.019 × 0.025-in SS, and 0.019 × 0.025-in NiTi. Each bracket/archwire combination was tested 10 times in the dry state at an ambient temperature of 34°C. Results: Low-friction ligatures with round archwires showed statistically significantly lower frictional resistance than did conventional ligatures. When coupled with 0.016 × 0.022-in NiTi and SS, no statistically significant difference was observed among the four groups. When coupled with 0.017 × 0.025-in archwires, low-friction ligatures showed statistically significantly greater frictional resistance than was seen with conventional ligatures. When coupled with 0.019 × 0.025-in NiTi, low-friction ligatures showed statistically significantly greater frictional resistance than did conventional ligatures, but no difference among the four groups was observed with the 0.019 × 0.025-in SS. No significant difference was assessed among low-friction ligatures of different sizes. Conclusion: Low-friction ligatures show lower friction when compared with conventional ligatures when coupled with round archwires, but not when coupled with rectangular ones.
39
Prapai, Jirapat, Monnapas Morakotjinda, Thanyaporn Yotkaew, Bhanu Vetayanukul, Ruangdaj Tongsri, Panya Kamsuwan e Masahiko Yoshino. "Tribological Properties of PM Cu-Based Dry Friction Clutch". Key Engineering Materials 545 (marzo 2013): 163–70. http://dx.doi.org/10.4028/www.scientific.net/kem.545.163.
Testo completoAbstract (sommario):
Sintered Cu-based frictional materials were developed by using powder metallurgy (PM) method. The materials are aimed for application in a passenger car as a dry friction clutch. Effects of sintering temperature and composition on mechanical and tribological properties were determined. It was found that improper frictional material formulations caused inferior properties, particularly when the sintering temperatures were increased. Admixing of high Sn content (8 wt. %) resulted in decreases of sintered density and hardness with increasing sintering temperature. High Sn contents caused swelling of the sintered materials. Tribological properties (friction coefficient and wear rate) of the sintered specimens of the investigated materials were insensitive to sintering temperatures in the range of 800-950 °C but they were strongly influenced by chemical compositions. Addition of 3 wt. % graphite lowered the friction coefficient, which subsequently lowered the wear rate of the sintered material. To increase friction coefficient, one of the crucial properties of the dry friction clutch, of the sintered Cu-based frictional materials, two approaches were employed. In the first approach, substitution of graphite by SiO2 powders could improve the material friction coefficient. In the second approach, decreases of graphite content from 3 to 1 wt. % and of Sn content from 8 to 2 wt. % were conducted. The latter approach not only improved friction coefficient but also improved sintered density and hardness of the Cu-based frictional materials.
40
Wang, Xingming, Ping Chen, Zhenhua Rui e Fanyao Jin. "Modeling Friction Performance of Drill String Torsional Oscillation Using Dynamic Friction Model". Shock and Vibration 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/4051541.
Testo completoAbstract (sommario):
Drill string torsional and longitudinal oscillation can significantly reduce axial drag in horizontal drilling. An improved theoretical model for the analysis of the frictional force was proposed based on microscopic contact deformation theory and a bristle model. The established model, an improved dynamic friction model established for drill strings in a wellbore, was used to determine the relationship of friction force changes and the drill string torsional vibration. The model results were in good agreement with the experimental data, verifying the accuracy of the established model. The analysis of the influence of drilling mud properties indicated that there is an approximately linear relationship between the axial friction force and dynamic shear and viscosity. The influence of drill string torsional oscillation on the axial friction force is discussed. The results indicated that the drill string transverse velocity is a prerequisite for reducing axial friction. In addition, low amplitude of torsional vibration speed can significantly reduce axial friction. Then, increasing the amplitude of transverse vibration speed, the effect of axial reduction is not significant. In addition, by involving general field drilling parameters, this model can accurately describe the friction behavior and quantitatively predict the frictional resistance in horizontal drilling.
41
Arakawa, Sota, Hidekazu Tanaka e Eiichiro Kokubo. "Collisional Growth Efficiency of Dust Aggregates and Its Independence of the Strength of Interparticle Rolling Friction". Astrophysical Journal 939, n. 2 (1 novembre 2022): 100. http://dx.doi.org/10.3847/1538-4357/ac96e1.
Testo completoAbstract (sommario):
Abstract The pairwise collisional growth of dust aggregates consisting of submicron-sized grains is the first step of planet formation, and understanding the collisional behavior of dust aggregates is therefore essential. It is known that the main energy dissipation mechanisms are the tangential frictions between particles in contact, namely, rolling, sliding, and twisting. However, there is great uncertainty for the strength of rolling friction, and the dependence of the collisional growth condition on the strength of rolling friction was poorly understood. Here we performed numerical simulations of collisions between two equal-mass porous aggregates with various collision velocities and impact parameters, and we also changed the strength of rolling friction systematically. We found that the threshold of the collision velocity for the fragmentation of dust aggregates is nearly independent of the strength of rolling friction. This is because the total amount of the energy dissipation by the tangential frictions is nearly constant even though the strength of rolling friction is varied.
42
Kang, Chao, Yaoyao Shi, Tao Yu, Pan Zhao, Bo Deng, Zhen Chen e Hongji Zhang. "Experimental investigation of friction between prepreg tape and compaction roller for prepreg tape hoop winding". Journal of Reinforced Plastics and Composites 37, n. 12 (30 marzo 2018): 853–62. http://dx.doi.org/10.1177/0731684418764018.
Testo completoAbstract (sommario):
As an inevitable issue in the filament winding technology, the process-induced friction has gained increasing attention. The purpose of this study is to illustrate the experimental investigation of friction between prepreg tape and hot compaction roller in prepreg tape hoop winding system. Based on the modified version of Howell’s equation, the friction model is established to offer an indirect method for measuring the frictional coefficient during the actual composite fabricating process. Three types of prepreg tapes, namely T300/Y69 unidirectional prepreg tape, T300/DFQS-3 and BWT260-82/DFQS-3 orthogonal prepreg tapes are selected to discuss the effect of process parameters on friction under different processing conditions. The experimental results reveal that the friction behavior transfers from resin-dominated friction to fiber-governed friction as the temperature rises. Besides, acceleration of the spindle speed on the frictional coefficient can be markedly improved due to the increase of resin strain rate. Meanwhile, the fiber has a stronger ability to increase friction than resin. It is also observed that the friction plays a role in amplifying the winding tension by comparing the winding tension with the outgoing winding tension.
43
Zhang, Zixin, Zhuangzhuang Chu e Xuli Zhu. "Frictional effect of spherical convex textured rigid bodies sliding on smooth PDMS". E3S Web of Conferences 145 (2020): 02055. http://dx.doi.org/10.1051/e3sconf/202014502055.
Testo completoAbstract (sommario):
Surface texturing was applied to flexible friction couples to improve their tribological behavior. Spherical convex texture was fabricated on the surface of photosensitive resin by stereolithography (SLA), the friction coefficient between the textured resin sample and smooth polydimethylsiloxane (PDMS) under the conditions of low sliding speed and dry friction was measured using a self-made frictional test bench. It was found that surface texture is capable of reducing friction at low applied normal load compared with the non textured friction couple, as well as increasing friction at high load, in addition, smaller texture radii tend to increase friction. At last, the friction mechanism of the textured flexible friction couple was discussed by establishing a mechanical model.
44
D. Ghanim, Sattam, Qais ѕ. Banyhussan e Thulfiqar А. Aboaljus. "THE PUSHOUT STRENGTH OF CONCRETE PAVEMENT SLAB AND CLAY SOIL LAYERS". Journal of Engineering and Sustainable Development 25, Special (20 settembre 2021): 3–224. http://dx.doi.org/10.31272/jeasd.conf.2.3.22.
Testo completoAbstract (sommario):
The frictional forces between the concrete slab and base has been combined with the movements of the horizontal slab that have been induced by variations of the moisture and temperature in concrete slabs. The frictional drag that acts on the slab bottom as a result of base friction is in an opposite horizontal slab displacement direction, and resist movements of the horizontal slab. A condition of smoother interface provides lower resistance to slab movement. On the other hand, rough interfaces are beneficial in the reduction of the load-related stresses. As bonding degree between slab and foundation affects the friction that has been mobilized at interface, a realistic evaluation of friction of the interface is required for the rational designs of the concrete pavement. In this work, push-off test has been performed. Based upon results of the friction tests, the friction characteristics of concrete and soil have been researched. The parameters that influence the maximal displacement and friction coefficient are (interface state, rate of movement) for friction and (rate of movement, interface condition) for the displacements, respectively. Finally, once the applied force reaches a stable state, the frictional force increases dramatically. The most important influence on this force is the interface state, which is accompanied by movement rate. The change of the interface from a smooth to a rough surface increases the overall coefficient of friction.
45
Wang, Yanzhong, Kai Yang e Xiangyu Wu. "Structural Design and Friction Performance Test of a New Conical Groove Friction Disks in Wet Clutch". Applied Sciences 11, n. 16 (5 agosto 2021): 7231. http://dx.doi.org/10.3390/app11167231.
Testo completoAbstract (sommario):
Wet clutch transmits its power by the friction torque between friction and separate disks. Conical groove friction disk is a new attempt in Wet clutch. Its configurations allow significant enhancement of torque delivery performances, compared with the traditional plane friction disk. In order to study the frictional performances of the conical groove friction configuration, the friction coefficient calculation model of conical groove friction disk was established, and experimental investigation was used to measure the friction coefficient under sliding velocity conditions. The influence of configuration parameters: cone heights and angles on friction coefficients were evaluated in a typical variable speed test. The results indicated that configuration parameters can affect friction performance in a constant speed period. The equivalent radius can directly describe the friction region of a conical groove friction disk. The constant speed test can be a useful method.
46
Shapovalov, Vladimir, Petr Shcherbak, Pavel Kharlamov, Tatiana Sajamova e Denis Ryabysh. "Improving the energy efficiency of power transmissions of a rolling stock on the basis of dynamic anisotropy of frictional contact". E3S Web of Conferences 104 (2019): 01002. http://dx.doi.org/10.1051/e3sconf/201910401002.
Testo completoAbstract (sommario):
The analysis showed the following tendencies of development and energy efficiency of designs of gearboxes for track machines: provision of a maximum level of efficiency, removal of rupture of a stream of the passed capacity, provision of a high level of reliability, decrease of power input on gearbox work, provision of convenience, simplicity of service and steering, engine braking maintenance, and also maintenance of a relatively low cost. The above-mentioned tasks are performed by including clutch pinion gears with the built in frictional amplifier elements in an automatic gearbox, and also during the effect of dynamic anisotropy of frictional bonds. Besides a torque transfer, the clutch gear carries out a safety clutch function. That means that there is sliding at a high rotational power. Factor of strengthening of the given link is Кstr → ∞ due to occurence of dynamic anisotropy of frictional bonds. Physical and mechanical characteristics of contacting surfaces are formed in the course of dynamic interaction of roughnesses in friction units at modes of dry and boundary friction. Essential-nonlinear friction processes, interconnected with dynamic processes on the contact area, define values of target characteristics of frictional system. They can fluctuate in a very wide range. The friction factor fmp for the same friction units at preservation of constant conditions and friction parameters can vary from zero to infinity that is an essence of dynamic anisotropy of frictional bonds.
47
Baum, Martina J., Lars Heepe e Stanislav N. Gorb. "Friction behavior of a microstructured polymer surface inspired by snake skin". Beilstein Journal of Nanotechnology 5 (24 gennaio 2014): 83–97. http://dx.doi.org/10.3762/bjnano.5.8.
Testo completoAbstract (sommario):
The aim of this study was to understand the influence of microstructures found on ventral scales of the biological model, Lampropeltis getula californiae, the California King Snake, on the friction behavior. For this purpose, we compared snake-inspired anisotropic microstructured surfaces to other microstructured surfaces with isotropic and anisotropic geometry. To exclude that the friction measurements were influenced by physico-chemical variations, all friction measurements were performed on the same epoxy polymer. For frictional measurements a microtribometer was used. Original data were processed by fast Fourier transformation (FFT) with a zero frequency related to the average friction and other peaks resulting from periodic stick-slip behavior. The data showed that the specific ventral surface ornamentation of snakes does not only reduce the frictional coefficient and generate anisotropic frictional properties, but also reduces stick-slip vibrations during sliding, which might be an adaptation to reduce wear. Based on this extensive comparative study of different microstructured polymer samples, it was experimentally demonstrated that the friction-induced stick-slip behavior does not solely depend on the frictional coefficient of the contact pair.
48
Qiu, Ming Ming, Han Zhao e Fa Ming Sha. "The Simulation Research of Dual Clutch Transmission's Starting Process Based on Dynamic Friction Coefficient". Applied Mechanics and Materials 401-403 (settembre 2013): 320–25. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.320.
Testo completoAbstract (sommario):
Introduce the dynamic friction coefficient of clutch friction plate. Establish Mathematical model of starting process, carried out vibration analysis for frictional sliding process systematically, validated the analysis using Matlab/simulink software. Meanwhile, compared with the starting process by static friction coefficient. The results show that using dynamic friction coefficient to analyse starting process conforms to the actual working condition.
49
Numazaki, Kento, Masatoshi Takahashi, Arata Ito, Yukyo Takada e Itaru Mizoguchi. "The Effect of Electroless Nickel–Polytetrafluoroethylene Coating on the Frictional Properties of Orthodontic Wires". Metals 14, n. 2 (9 febbraio 2024): 213. http://dx.doi.org/10.3390/met14020213.
Testo completoAbstract (sommario):
In orthodontic treatment, to achieve efficient tooth movement, it is important to reduce the frictional force between the wire and the bracket, especially the binding friction that occurs when the angle between the wire and the bracket is large. Electroless nickel–polytetrafluoroethylene (Ni-PTFE) coating is a coating technology used to deposit PTFE particles with a low coefficient of friction on the coating surface to provide a low-friction surface for metallic materials. The purpose of this study was to investigate the effect of Ni-PTFE-coated orthodontic wires on the frictional force between brackets. The surface morphology, surface roughness, and frictional properties of Ni-PTFE-coated stainless steel wires and Ni-Ti wires were evaluated. The results demonstrate that the Ni-PTFE coating reduced the frictional force between the orthodontic wires and brackets, despite the increased surface roughness. Even when the angle between the wire and bracket was increased, assuming binding friction, the frictional force was reduced by the Ni-PTFE coating. This suggests that the friction between the wire and the bracket was suppressed by the PTFE particles deposited on the wire surface in contact with the bracket.
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Liu, Chuan-Ping, Chuan-Yu Wu, Chao Zheng e Li Wang. "Effects of friction on stress on a plate penetrating into granular media". Physics of Fluids 33, n. 5 (maggio 2021): 053315. http://dx.doi.org/10.1063/5.0049262.
Testo completoAbstract (sommario):
The penetration of a plate into granular media was analyzed, and the effects of particle–plate and particle–particle frictions, penetration direction, and initial plate orientation were examined. Results showed that stress was directly proportional to immersion depth for frictionless particles but jumped at the bed surface and then increased linearly for frictional particles. Moreover, stress was mostly independent of the penetration direction when the plate was frictionless. However, initial orientation always had an effect regardless of whether the plate was frictional or frictionless. Furthermore, a theoretical model was developed for stress analysis. This model revealed that friction on the plate essentially affected stress via changing the push angle of the particles that were in contact with the plate.